Sear device for an automatic firearm



Jgn. 8, 1957 E. c. LTEE 2,776,501

l SEAR DEVICE FOR AN AUTOMATIC FIREARM Filed Nov. 25, 195,3 4 Sheets-Sheet l IN VEN TOR.

:Ecwnrd E LEE ,aTrb/e'NEYS Jan. 8, 1957 E. c. LEE

SEAR DEVICE FOR AN AUTOMATIC FIREARM 4 Sheets-Sheet 2 Filed Nov. 25. 135s INVENToR. E wurd l: LE E fnawfaam HTTOENEYS Jan; 8, 1957 E. c. LEE 2,776,601

SEAR DEVICE FOR AN AUTOMATIC FIREARM Filed Nov. 25. 1953 4 Sheets-Sheet 3 Fil-21H5..

INLV EN TOR.

ATM/@A15 Ys Jan. 8, 1957 E, c, LEE 2,776,601

SEAR DEVICE FOR AN AUTOMATIC FIREARM Filed Nov. 25, 1953 4 Sheets-Sheet 4 IN V EN TOR.

HTTOENE YS United States Patent O SEAR DEVICE FOR AN AUTOMATIC FIREARM Edward C. Lee, Detroit, Mich., assignor to the United States of America as represented by the Secretary of the Army Application November 25, 1953, Serial No. 394,524

4 Claims. (Cl. 89-136) This invention relates to automatic firearms wherein a firing member is resiliently mounted for slidable movement in a reciprocating bolt and is particularly directed to means for locking the 'firing member in a cocked position and for the release thereof when the bolt is in a battery position.

In automatic firearms of the type disclosed in Patent No. 1,628,226 to lohn M. Browning, there is provided a spring-biased firing member which is slidably mounted for longitudinal movement between a cocked and a firing position in a reciprocal bolt. The firing member is retained in the cocked position by the engagement thereof with a springbiased sear which is slidably mounted in the bolt for vertical recirprocating movement therein. When the bolt is moved to the battery position, the Sear, depressed by suitable means, releases the firing member therefrom which moves forwardly under the bias of its spring to discharge a chambered cartridge. During the ensuing recoil movement of the bolt, a cocking lever which is pivotally mounted therein is rotated to force the ring member rearwardly into reengagement with the sear which in the meantime has been returned from the depressed position by the bias of the spring. During counter-recoil movement of the bolt, the cooking lever is rotated free of the firing member whereupon the latter is free to move forwardly when released by the sear to eltect another cycle of operation.

In firing mechanisms of this type, considerable trouble has been encountered in providing positive engagement between the sear and the tiring member so as to prevent a premature release thereof. Failure of the Sear to maintain engagement with the firing member results in either premature discharge of the cartridge with corresponding disastrous results, or failure to ignite the cartridge through lack of a proper blow on the primer when the bolt is in battery position. The latter malfunction is the type most usually experienced with firing mechanisms of this type.

Accordingly, it is an object of this invention to provide in an automatic firearm bolt a pivotally mounted sear having positive engagement with a tiring member.

It is a further object of this invention to provide in an automatic firearm bolt a sliding member which both actuates the sear and locks the sear in engagement with the tiring member.

Another object of this invention is to provide in an automatic firearm bolt a trigger which moves a sliding member to unlock the sear from engaged position and then directly engages the sear for actuation thereof.

It is the specific object of this invention to provide for an automatic firearm bolt an improved sear device wherein positive engagement is provided between the sear and the tiring member and the sear is locked in engagement with the firing member by a sliding sear actuating member until the actuating member is actuated to release the firing member.

The specific nature of the invention as well as other objects and advantages thereof will clearly` appear from a 2,776,601 Patented Jan. 8, 1957 ICC description of a preferred embodiment as shown in the accompanying drawings in which:

Fig. l is a longitudinal cross-sectional view of a firearm bolt showing the firing member in retracted position;

Fig. 2 is a fragmentary view similar to Fig. 1 but showing the firing member in fired position;

Fig. 3 is an enlarged perspective view of the trigger pin and trigger pin stop in assembly relationship;

Fig. 4 is an enlarged exploded view of the sear and firing member mechanism;

Fig. 5 is a cross-sectional top view showing thev means for mounting the sear and for compressing the firing member spring;

Fig. 6 is an end View of the bolt partially cross-sectioned showing the sear in locked engaged position;

Fig. 7 is a view similar to Fig. 6 but showing the sear partially unlocked by the trigger pin and the sear engaged thereby;

Fig. 8 is a view similar to Figs. 6-7 but showing the sear fully depressed by the trigger pin;

Fig. 9 is a view similar to Fig. l but showin-g an alternate means of mounting the tiring member and scar; and

Fig. 10 is a View similar to Fig. 2 of the alternate means of mounting the firing member and sear.

illustrated in the drawings is a bolt 12 of the wellknown Browning type. Provided in the rear end of such bolt is a rectangular cavity 13 which is traversed at right angles and at approximately the top side thereof by a rearwardly opening T-slot 1S. Disposed forwardly of cavity 13 and communicating therewith is a longitudinal well 16 and a bore 17 of smaller diameter which extends axially from the end wall thereof to form an annular shoulder 18. Extending forwardly from a bottom side 19 of cavity 13 is a rectangular channel 20 which is arranged parallel with well 16 and 'bore 17 and communicates longitudinally therewith. A recess 21 in the top side of bolt 12 is arranged to communicate with well 16 by means of a vertically disposed orifice 9.

A sear 22 having a body portion 23 receivable by cavity 13 and a lever portion 24 receivable by channel 20 is mounted in bolt 12 by means hereinafter described for pivotal movement between an engaged and a disengaged position. Mounted in T-slot 15 for slidable movement therein is a sear slide 25. A firing member 26 is mounted in well 16 and bore 17 for reciprocal movement between a sear engaging position and a firing position, and a cocking lever 27 is pivotally mounted in orifice 9 on a lateral pin 28 with the bottom end receivable by a slot 32 in t`1ring member 26 and the top end engageable with a V-slot 8 in the top plate bracket of the receiver during the initial recoil of bolt 12 whereby firing member 26 is moved from the tiring position to the sear engaging position.

Firing member 26 is provided with a striker portion 29 receivable by bore 17 and an extension portion 30 of larger diameter receivable by well 16. The forward end of extension 31) forms an annular ledge 31 at the junction thereof with striker 29, and such ledge is engageable with shoulder 18 to establish the firing position of firing member 26.

Provided in extension 30 forwardly of slot 32 is a longitudinal hole 34, adapted to receive a coiled compression spring 35. The front end of spring 35 abuts a vertical pin 36 provided through the front end of extension 30 and the rear end of a plunger 37 slidably mounted in hole 34. Plunger 37 is provided with a rod portion 38 received by spring 35 and a head portion 39 which is engaged by the end of such spring. A crevice 44 of similar Width as slot 32 bifurcates the rear end of head portion 39 and is alignable with such slot when plunger 37 is in its rearmost position. The rearward movement of plunger 37 is stopped by shoulder 40, formed by the junction of hole 34 with slot 32, which engage the bifurcated ends of head portion 39. A pin 41 is mounted laterally through bolt 12 and passes through extension 36 in longitudinal openings 42 therein to permit movement of firing member 26 between sear engaging position and firing position. Arcuate cutouts 43 are provided in the bifurcated ends of head portion 39 to receive pin 41 whereby crevice 44 is maintained in alignment with slot 32 and plunger 37 is anchored to bolt 12 whereby spring 35 is compressed when cooking lever 27 moves firing member 26 rearwardly.

The rear end of extension 30 is slabbed as noted by 4S and depending from the rear end thereof is a laterally disposed lip portion 46 having a vertical scar engaging surface 47. Extending forwardly from slabbed portion 45 is a rectangular chasm 48 which provides communication with hole 34. Chasrn 48 pivotally and slidably receives lever portion 24 of sear 22. Lever portion 24 is terminated by a boss 49 provided with a laterally disposed aperture 50 which receives pin 41 for rotatable support of scar 22.

Body portion 23 of seal' 22 is essentially L-shaped and provided on the top side of foot portion 53 thereof is a raised portion 51 whereby there is formed a substantially vertical hook portion 52 engageable with sear engaging surface 47 on firing member 26. Raised portion 51, further, provides slidable support for lip portion 46 of firing member 26 when such firing member is out of sear engaged position. Provided on the front side of leg 54 of body portion 23 is a forwardly projecting truncated triangular lug 55. The sides of leg 54 are indented as shown by 56 and formed thereby are downwardly facing look surfaces 57. A coiled compression spring S is accommodated in a hole 33, which extends upwardly from the bottom side of body portion 23, and bears against bottom side 19 of cavity 13 to normally bias sear 22 up wardly, positioning hook portion 52 ready to engage scar engaging surface 47 of firing member 26 when such tiring member is released by cooking lever 27 during counterrecoil of bolt 12.

As has also hereinbefore been described, sear slide 25 is slidably mounted in Taslot 15. The rear side of sear slide 25 is cut away, as noted by 62, to permit slidable movement thereof in front of sear 22 and provided in such cutout portion are communicating vertically opposed recesses 59. Recesses 59 are similar in configuration to but slightly larger than lug S5 which is arranged to be receivable in one of such recesses whichever of the horizontal sides of sear slide 25 is placed on top.

Recesses 59 divide the rear side of sear slide 25 into a short portion 64 and a long portion 65 and are so arranged that when one is occupied by lug 55, long portion 65 projects outwardly from one end of T-slot so as to be engageable by a trigger device (not shown). When it is desired for long portion 65 to be engaged by a trigger device on the opposite side of bolt 12, sear slide is assembled in T-slot 1S so that the opposite recess 59 is occupied by lug 55. Provided on short portion 64 is a tongue portion 60 which is receivable in the communicating one of the indents 56 to engage locking surface 57 thereof when the adjacent side of the occupied recess 59 engages the cooperating side of lug 55 and is nearly free thereof when the opposite side of such recess iirst cngages the cooperating side of such lug. Provided in long portion 65 within cutaway 62 is a recessed slideway 61 which inclines downwardly from one of the horizontal sides of scar slide 25 so as to be parallel with the opposite side of the upwardly adjacent recess 59.

Mounted for slidable movement in a vertical hole 80 provided between the top side of bolt 12 and cutaway slideway 61. Operating surface is so arranged that when tongue portion 6i? is fully inserted in the selected one of the indents 56 the bottom part of such operating surface is engaged with the upper portion of slideway 6l, as best shown in Fig. 6, and when trigger pin 81 is pressed downwardly the engagement of operating surface 85 with slideway 61 cams sear slide 25 in T-slot 1S so as to move tongue portion 60 free of the cooperating indent 56, as best shown in Fig. 7. Shoulders 83 are so arranged that, when tongue portion 66 is nearly free of indent 56, the rear one of such shoulders contacts the top surface of body portion 23 of Sear 22 whereby continued downward movement of trigger pin 81 completes the unlocking of such sear and moves such sear downwardly to disengage tiring member 26 therefrom. The opposite shoulder 83 provides clearance for the movement of trigger pin 81 past the front side of sear slide 25. When soar slide 25 is assembled so that the opposite recess 59 is occupied by lug 55, trigger pin 3l is rotated 180 so that operating surface 85 slidably engages the adjacent side of the upper one of the recesses 59.

Mounted in recess 21 is a trigger pin looking member 86 having a pin portion 87 rotatably mounted in a vertical hole 88 provided in the bottom side of such recess and an arm portion 89 which when in locking position engages the side of recess 21 and lies adjacent orifice 9. One end of arm 89 arches upwardly to provide a stop for cooking lever 27. The opposite end of such arm S9 is receivable by one of a pair of planar based notches 91 in trigger pin 81 whereby such trigger pin is secured against rotation and the vertical movement thereof is limited. Notches 91 are so arranged that arm 89 is receivable in one of such notches, whichever position trigger pin 81 is assembled in bolt 12. Assembly of cooking lever 27 in orifice 9 engageably secures locking member 86 in the occupied notch 91.

Provided in the front side of T-slot 15 are a pair of longitudinal holes 94 spaced laterally apart equidistant from the center of such T-slot. selectively receivable in one of such holes is a rod member 95 having a seat portion 96 which receives one end of a coiled compression spring 97. The other end of spring 97 is received by a hole 98 provided laterally in short portion 64 of sear slide 25 whereby tongue 6i) is biased into lock position in indent 56. When sear slide 25 is reversed in T-slot 15, rod 95 is inserted in the opposite hole 94 with spring 97 biasing tongue 60 into the oppostie indent 56.

When the firearm incorporating the above-described sear mechanism is fired, bolt 12 is recoiled causing cocking lever 27, pivotally mounted therein, to be rotated from the position shown in Fig. 2 to that shown in Fig. 1 by the engagement of the top portion thereof with V-slot 8 in the top plate bracket of the firearm receiver. The rotation of cooking lever 27 forces firing member 26 rearwardly by the engagement of the bottom end of such cooking lever with the rear wall of slot 32 in extension 30 of such tiring member. As firing member 26 moves rearwardly, lip portion 46 thereon slidably moves on raised portion 51 of sear 22 until sear engaging surface 47 comes adjacent hook portion 52 whereupon sear 22 is permitted to pivot upwardly on pin 4l under the bias of spring 58 ready to engage such firing member when released by cooking lever 27. On the counter-recoil of bolt 12, cooking lever 27 is rotated by engagement with V-slot 8 from the position it was moved to during recoil to the position shown in Fig. 2, whereby ring member 26 is permitted to move slightly forward to be engaged by sear 22. Continuing counter-rotation of cooking lever 27 swings the bottom end thereof free of the rear wall of slot 32, permitting tiring member 26 to be driven forwardly by spring 35 to lire a chambered cartridge when bolt 12 is in battery and such ring member is released by sear 22.

When sear 22 is in engaged position, tongue 60 in Sear slide 25 is aligned with the adjacent indent 56 in sear 22 and is urged thereinto by spring 97 whereby the engagement of such tongue with lock surface 57 prevents accidental, premature depression of such sear to release tiring member 26.

The sear release mechanism shown herein is adaptable for operation from the top or either side of the firearm. When operated from the top, a vertical force is directed against trigger pin 81. When operated from the side a transverse force is directed against the protruding end of sear slide 25. Sear slide 25 can be assembled as here- 7inbefore described so that long perion 65 thereof protrudes from either side of T-slot 15.

When the weapon is to be fired from the top of the receiver, trigger pin 81 and sear slide 25 are so arranged that the diagonally inclining operating :surface 85 of such trigger pin and the mating slideway 61 of such sear slide are in slidable relationship whereby a downward force directed on the protruding end of such trigger pin cammingly moves such sear slide along T-slot 15.

As has hereinbefore been described, lug 55 of sear 22 is slightly smaller than the occupied recess 59 `of sear slide 25 and is `so arranged therewith that when tongue 60 is fully received in indent 56, the side of such lug adjacent such tongue is engaged with the corresponding side of such recess. During the initial downward movement of trigger pin 81, sear slide 25 is cammed thereby along T-slot against the bias of spring 97 until the opposite sides of occupied recess 59 and lug 55 engage and the rear shoulder 83 of such trigger pin contacts the top of sear 22 at which time tongue 60 is moved nearly out of indent 56. Continuing downward pressure of trigger pin 81 fully unlocks tongue 60 from lock surface 57 and sear 22 is simultaneously depressed by engagement of shoulder 83 thereagainst to release tiring member 26.

When it is desired to tire the weapon from the side, force is exerted by suitable means on the protruding end of sear slide 25. During the initial movement of sear slide 25, occupied recess 59 therein is moved from engagement with one side `of lug 55 to engagement with the other. Further movement of sear slide 25 forces the engaged side of recess 59 against the engaged side of lug 55 whereby sear 22 is cammingly depressed to disengage tiring member 26 therefrom.

When sear slide 25 is reversed so that the weapon may be operated from the opposite side, whereby short portion 64 comes adjacent trigger pin 81, such trigger pin is rotated 180 so that operating surface 85 thereof slidably engages the mating side of the upwardly disposed recess 59 for operating the sear mechanism in the same manner as when engaged with slideway 61. Hence, the firearm may be selectively operated from the top and one of the sides thereof regardless of which position sear slide 25 is assembled to bolt 12.

In Figs. 9 and 10 there are shown in an alternate embodiment, a ring member 99, a sear 100 and a trigger pin locking member 101 which are similar to the previously described tiring member 26, sear 22 and trigger pin locking member 84 except as hereinafter noted. In the present embodiment the pin portion of trigger pin locking member 101, noted here by 102, extends downwardly through hole 88 and slot 32 of ring member 99 with the bottom and receivable in a hole 108 to provide rigidity to such pin portion. Firing pin spring 35 is arranged to bear directly on pin portion 102 and thereby bias ring member 99 to firing position. Herein, pin 41 is mounted transversely in bolt 12 rearwardly of pin portion 102. Elongated openings 109 are provided in extension 104 of tiring member 99 to receive pin 41 therethrough and are arranged to permit reciprocal movement of such tiring member. Sear 100 is mounted for rotational movement on pin 41 and functions in cooperation with sear slide 25 in the same manner as sear 22.

From the foregoing description, it is clearly apparent that there is here provided a sear mechanism of superior design. It is obvious that by the tiring member being in slidable engagement with the sear when out of engaged position the shock of engagement encountered in conventional designs has been eliminated. It is further obvious that the means of locking the sear in engaged position is simple, rugged and effective. Moreover, the means of operating the sear and locking member from the top side of the bolt is simple in construction, rugged and easy to manufacture.

Although a particular embodiment of the invention has been described in detail herein, it is evident that many variations may be devised within the spirit and scope thereof and the followng claims are intended to include such variations.

I claim:

l. In a bolt for a firearm, a pin mounted transversely through the bolt, a firing member having a longitudinal hole with an end wall mounted on said pin for slidable movement between a firing position and a rectracting position, a spring mounted in said hole between said end wall and said pin for biasing said firing member to said retracting position, a sear for releasa'bly holding said tiring member in said retracting position, said sear being mounted on said pin for pivotal movement between a holding position and a disengaging position, a triangularlike lug on said sear, a slidable member interchangeably mounted in a transverse T-slot in the bolt for sliding movement in response to an outside force from either side of the bolt, a tongue portion on said slidable member selectively cooperable with a pair of indents in opposite sides of said sear for releasably lock-ing said sear in said holding position, said slidable member being provided with a pair of vertically opposed recesses having inclining sides, said recesses 'being similar in configuration to but larger than said lug, said lug being selectively receivable by said recesses and being so cooperable with said sides thereof that said tongue portion is: movable in and out of cooperation with the selected one of said indents during movement of said lug vbetween said sides and to sub sequently cooperate with said sides to move said sear to said disengaging position, and a vertically disposed trigger pin slidably mounted in the bolt, said trigger pin being provided with a tenon projecting from a pair of shoulders to be received by a recessed slideway in said slidable member, said tenon being provided with an inclining bottom portion cammingly cooperable with said slideway or one of said sides of the unoccupied one of said recesses whereby downward movement of said trigger pin carnmingly moves said slidable member to unlock said sear, and one of said shoulders being engageable with said sear when said tongue portion is free from the occupied one of said indents whereby further downward movement of said trigger pin moves said sear to said disengaging position.

2. In a lbolt `for a firearm, a spring-biased tiring member mounted for reciprocal movement between a tiring and a retracted position, lever means for actuating said tiring member to said retracted position, a sear for releasably latching said firing member in said retracted position, said sear being mounted for pivotal movement between a holding and a disengaging position and being provided with indent means, a slidable member mounted in the bolt for reciprocation between a locking and an actuating position, a tongue portion on said slidable member cooperable with said indent means for releasably locking said sear in said holding position when said slidable member is in said locking position, and inclining sides on said slidable member engageable with cooperat` ing inclining sides on said sear after said tongue portion is moved out of said indent means for cammingly actuating said sear to said disengaging position when said slidable member is moved to said actuating position.

3. In a bolt for a firearm, a firing member resiliently mounted for reciprocal movement between a firing and a retracted position, lever means for actuating said tiring member to said retracted position, a sear for releasably latching said firing member in said retracted position, said sear being mounted for pivotal movement between an engaging and a disengaging position and being provided with indent portions on opposite sides thereof, a substantially triangular lug portion on said sear, a slidable member reversibly mounted in the bolt for actuation from either side thereof from a locking to an actuating position, means for normally biasing said slidable member to said locking position, a tongue portion on said slidable member receivable by either one of said indent portions for locking said sear in said engaging position when said slidable member is in said locking position, substantially triangular recesses in said slidable member for receiving said lug portion and having yinclining sides engageable by said lug portion after said tongue portion is moved to unlock said sear to actuate said sear to said disengaging position during actuation of said slidable member to said actuating position, an inclining slideway in said slidable member, and a trigger pin slidably mounted in the bolt for cooperation with said slideway for actuating said slidable member suiciently to move said tongue portion from the cooperating one of said indent portions and subsequently directly engage said sear for moving said sear `to said disengaging position.

4. In a bolt for a rearm, a tiring member resiliently mounted for reciprocal movement between a tiring and a retracted position, lever means for actuating said firing member to said retracted position, a sear for releasably latching said firing member in said retracted position, said sear being mounted for pivotal movement between an engaging and a disengaging position and being provided with indent portions on opposite sides thereof, a truncated triangular lug portion on said sear, a slidable member reversibly mounted in the bolt for actuation from either side thereof from a locking to an actuating position, means for normally biasing said slidable member to said locking position, a tongue portion on said slidable member receivable by either one of said indent portions for locking said sear in said engaging position when said slidable member is in said locking position, substantially triangular recesses in said slidable member for receiving said lug portion and having inclining sides engageable by said lug portion after said tongue portion is moved to unlock said sear for actuation of said sear to said disengaging position during movement of said slidable member to said actuating position, an inclining slideway in said slidable member, a trigger pin slidably mounted in the bolt for actuation from the top `thereof to a depressed position, an inclining portion on said trigger pin cooperating with said slideway for actuating said slidable member suiciently to move said tongue portion from the cooperating one of said indent portions when said trigger pin is actuated to said depressed position, and shoulder portions on said trigger pin engageable with said sear for moving said sear to said disengaging position after said tongue portion is moved out of the cooperating one of said indent portions during actuation of said trigger pin to said depressed position.

References Cited in the le of this patent UNITED STATES PATENTS 1,846,156 Stange Feb. 23, 1932 1,949,418 Howard Mar. 6, 1934 2,462,114- Lochhead Feb. 22, 1949 2,562,801 Maillard `Tuly 31, 1951 

